Microsoft word - acetazolamide tablets usp 0305-1.doc
Acetazolamide Tablets USP DESCRIPTION Acetazolamide, an inhibitor of the enzyme carbonic anhydrase is a white to faintly yellowish white crystalline, odorless powder, weakly acidic, very slightly soluble in water and slightly soluble in alcohol. The chemical name for acetazolamide is N-(5-Sulfamoyl-1,3,4-thiadiazol-2-yl)-acetamide and has the following chemical structure:
Acetazolamide is available as oral tablets containing 125 mg and 250 mg of acetazolamide respectivelyand the following inactive ingredients: Lactose Monohydrate, Corn Starch, Gelatin, Glycerin, PurifiedWater, Talc, Sodium Starch Glycolate, and Magnesium Stearate. CLINICAL PHARMACOLOGY Acetazolamide is a potent carbonic anhydrase inhibitor, effective in the control of fluid secretion (e.g., some types of glaucoma), in the treatment of certain convulsive disorders (e.g., epilepsy) and in the promotion of diuresis in instances of abnormal fluid retention (e.g., cardiac edema).
Acetazolamide is not a mercurial diuretic. Rather, it is a nonbacteriostatic sulfonamide possessing achemical structure and pharmacological activity distinctly different from the bacteriostaticsulfonamides.
Acetazolamide is an enzyme inhibitor that acts specifically on carbonic anhydrase, the enzyme thatcatalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration ofcarbonic acid. In the eye, this inhibitory action of acetazolamide decreases the secretion of aqueoushumor and results in a drop in intraocular pressure, a reaction considered desirable in cases ofglaucoma and even in certain nonglaucomatous conditions. Evidence seems to indicate thatacetazolamide has utility as an adjuvant in the treatment of certain dysfunctions of the central nervoussystem (e.g., epilepsy). Inhibition of carbonic anhydrase in this area appears to retard abnormal,paroxysmal, excessive discharge from central nervous system neurons. The diuretic effect ofacetazolamide is due to its action in the kidney on the reversible reaction involving hydration of carbondioxide and dehydration of carbonic acid. The result is renal loss of HCO3 ion, which carries outsodium, water, and potassium. Alkalinization of the urine and promotion of diuresis are thus effected. Alteration in ammonia metabolism occurs due to increased reabsorption of ammonia by the renaltubules as a result of urinary alkalinization.
Placebo-controlled clinical trials have shown that prophylactic administration of acetazolamide at adose of 250 mg every eight to 12 hours (or a 500 mg controlled-release capsule once daily) before andduring rapid ascent to altitude results in fewer and/or less severe symptoms (such as headache, nausea,shortness of breath, dizziness, drowsiness, and fatigue) of acute mountain sickness (AMS). Pulmonaryfunction (e.g., minute ventilation, expired vital capacity, and peak flow) is greater in the acetazolamide
treated group, both in subjects with AMS and asymptomatic subjects. The acetazolamide treatedclimbers also had less difficulty in sleeping. INDICATIONS AND USAGE For adjunctive treatment of: edema due to congestive heart failure; drug-induced edema; centrencephalic epilepsies (petit mal, unlocalized seizures); chronic simple (open-angle) glaucoma, secondary glaucoma, and preoperatively in acute angle-closure glaucoma where delay of surgery is desired in order to lower intraocular pressure. Acetazolamide Tablets are also indicated for the prevention or amelioration of symptoms associated with acute mountain sickness in climbers attempting rapid ascent and in those who are very susceptible to acute mountain sickness despite gradual ascent. CONTRAINDICATIONS Acetazolamide therapy is contraindicated in situations in which sodium and/or potassium blood serum levels are depressed, in cases of marked kidney and liver disease or dysfunction, in suprarenal gland failure, and in hyperchloremic acidosis. It is contraindicated in patients with cirrhosis because of the risk of development of hepatic encephalopathy.
Long-term administration of acetazolamide is contraindicated in patients with chronic noncongestiveangle-closure glaucoma since it may permit organic closure of the angle to occur while the worseningglaucoma is masked by lowered intraocular pressure. WARNINGS Fatalities have occurred, although rarely, due to severe reactions to sulfonamides including Stevens- Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Sensitizations may recur when a sulfonamide is readministered irrespective of the route of administration. If signs of hypersensitivity or other serious reactions occur, discontinue use of this drug.
Caution is advised for patients receiving concomitant high-dose aspirin and acetazolamide, asanorexia, tachypnea, lethargy, coma and death have been reported. PRECAUTIONS General Increasing the dose does not increase the diuresis and may increase the incidence of drowsiness and/or paresthesia. Increasing the dose often results in a decrease in diuresis. Under certain circumstances, however, very large doses have been given in conjunction with other diuretics in order to secure diuresis in complete refractory failure. Information for Patients Adverse reactions common to all sulfonamide derivatives may occur: anaphylaxis, fever, rash (including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), crystalluria, renal calculus, bone marrow depression, thrombocytopenic purpura, hemolytic anemia, leukopenia, pancytopenia and agranulocytosis. Precaution is advised for early detection of such reactions and the drug should be discontinued and appropriate therapy instituted.
In patients with pulmonary obstruction or emphysema where alveolar ventilation may be impaired,acetazolamide, which may precipitate or aggravate acidosis, should be used only with caution.
Gradual ascent is desirable to try to avoid acute mountain sickness. If rapid ascent is undertaken andacetazolamide tablets are used, it should be noted that such use does not obviate the need for promptdescent if severe forms of high altitude sickness occur, i.e., high altitude pulmonary edema (HAPE) orhigh altitude cerebral edema.
Caution is advised for patients receiving concomitant high-dose aspirin and acetazolamide, as anorexia, tachypnea, lethargy, coma and death have been reported (see WARNINGS). Laboratory Tests To monitor for hematologic reactions common to all sulfonamides, it is recommended that a baseline CBC and platelet count be obtained on patients prior to initiating acetazolamide tablet therapy and at regular intervals during therapy. If significant changes occur, early discontinuance and institution of appropriate therapy are important. Periodic monitoring of serum electrolytes is recommended. Carcinogenesis, Mutagenesis, Impairment of Fertility Long-term studies in animals to evaluate the carcinogenic potential of acetazolamide have not been conducted. In a bacterial mutagenicity assay, acetazolamide was not mutagenic when evaluated with and without metabolic activation.
The drug had no effect on fertility when administered in the diet to male and female rats at a dailyintake of up to 4 times the recommended human dose of 1000 mg in a 50 kg individual. Pregnancy: Teratogenic Effect: Pregnancy Category C Acetazolamide, administered orally or parenterally, has been shown to be teratogenic (defects of the limbs) in mice, rats, hamsters and rabbits. There are no adequate and well-controlled studies in pregnant women. Acetazolamide should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus. Nursing Mothers Because of the potential for serious adverse reaction in nursing infants from acetazolamide, a decision should be made whether to discontinue nursing or to discontinue the drug taking into account the importance of the drug to the mother. Pediatric Use The safety and effectiveness of acetazolamide in pediatric patients has not been established. ADVERSE REACTIONS Adverse reactions, occurring most often early in therapy, include paresthesias, particularly a “tingling” feeling in the extremities, hearing dysfunction or tinnitus, loss of appetite, taste alteration and gastrointestinal disturbances such as nausea, vomiting and diarrhea; polyuria, and occasional instances of drowsiness and confusion.
Metabolic acidosis and electrolyte imbalance may occur.
Transient myopia has been reported. This condition invariably subsides upon diminution ordiscontinuance of the medication.
Other occasional adverse reactions include urticaria, melena, hematuria, glycosuria, hepatic insufficiency, flaccid paralysis, photosensitivity and convulsions. Also see PRECAUTIONS: Information for Patients for possible reactions common to sulfonamide derivatives. Fatalities have occurred although rarely, due to severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia and other blood dyscrasias (see WARNINGS). OVERDOSAGE No data are available regarding acetazolamide overdosage in humans as no cases of acute poisoning with this drug have been reported. Animal data suggest that acetazolamide is remarkably nontoxic. No specific antidote is known. Treatment should be symptomatic and supportive.
Electrolyte imbalance, development of an acidotic state, and central nervous effects might be expectedto occur. Serum electrolyte levels (particularly potassium) and blood pH levels should be monitored.
Supportive measures are required to restore electrolyte and pH balance. The acidotic state can usuallybe corrected by the administration of bicarbonate.
Despite its high intraerythrocytic distribution and plasma protein binding properties, acetazolamidemay be dialyzable. This may be particularly important in the management of acetazolamideoverdosage when complicated by the presence of renal failure. DOSAGE AND ADMINISTRATION Glaucoma: Acetazolamide should be used as an adjunct to the usual therapy. The dosage employed in the treatment of chronic simple (open-angle) glaucoma ranges from 250 mg to 1 g of acetazolamide per 24 hours, usually in divided doses for amounts over 250 mg. It has usually been found that a dosage in excess of 1 g per 24 hours does not produce an increased effect. In all cases, the dosage should be adjusted with careful individual attention both to symptomatology and ocular tension. Continuous supervision by a physician is advisable.
In treatment of secondary glaucoma and in the preoperative treatment of some cases of acutecongestive (closed-angle) glaucoma, the preferred dosage is 250 mg every four hours, although somecases have responded to 250 mg twice daily on short-term therapy. In some acute cases, it may bemore satisfactory to administer an initial dose of 500 mg followed by 125 or 250 mg every four hoursdepending on the individual case. A complementary effect has been noted when acetazolamide hasbeen used in conjunction with miotics or mydriatics as the case demanded. Epilepsy: It is not clearly known whether the beneficial effects observed in epilepsy are due to direct inhibition of carbonic anhydrase in the central nervous system or whether they are due to the slight degree of acidosis produced by the divided dosage. The best results to date have been seen in petit mal in children. Good results, however, have been seen in patients, both children and adult, in other types of seizures such as grand mal, mixed seizure patterns, myoclonic jerk patterns, etc. The suggested total daily dose is 8 to 30 mg per kg in divided doses. Although some patients respond to a low dose, the optimum range appears to be from 375 to 1000 mg daily. However, some investigators feel that daily doses in excess of 1 g do not produce any better results than a 1 g dose. When acetazolamide tablets are given in combination with other anticonvulsants, it is suggested that the starting dose should be 250 mg once daily in addition to the existing medications. This can be increased to levels as indicated above.
The change from other medications to acetazolamide should be gradual and in accordance with usualpractice in epilepsy therapy. Congestive Heart Failure: For diuresis in congestive heart failure, the starting dose is usually 250 to 375 mg once daily in the morning (5 mg/kg). If, after an initial response, the patient fails to continue to lose edema fluid, do not increase the dose but allow for kidney recovery by skipping medication for a day. Acetazolamide tablets yield best diuretic results when given on alternate days, or for two days alternating with a day of rest.
Failures in therapy may be due to overdosage or too frequent dosage. The use of acetazolamide doesnot eliminate the need for other therapy such as digitalis, bed rest, and salt restriction. Drug-Induced Edema: Recommended dosage is 250 to 375 mg of acetazolamide once a day for one or two days, alternating with a day of rest. Acute Mountain Sickness: Dosage is 500 mg to 1000 mg daily, in divided doses. In circumstances of rapid ascent, such as in rescue or military operations, the higher dose level of 1000 mg is recommended. It is preferable to initiate dosing 24 to 48 hours before ascent and to continue for 48 hours while at high altitude, or longer as necessary to control symptoms. Note: The dosage recommendations for glaucoma and epilepsy differ considerably from those for congestive heart failure, since the first two conditions are not dependent upon carbonic anhydrase inhibition in the kidney which requires intermittent dosage if it is to recover from the inhibitory effect of the therapeutic agent. HOW SUPPLIED Acetazolamide Tablets USP, 125 mg - White, round, scored in half, on one side, “T52” engraved on the other side are supplied as follows: NDC 51672-4022-1 - Bottles of 100 Tablets 250 mg - White, round, scored in quarters, on one side, “T53” engraved on the other side are supplied as follows: NDC 51672-4023-1 - Bottles of 100 Tablets Store at 20˚-25˚C (68˚-77˚F). Excursions permitted to 15˚-30˚C (59˚-86˚F) [see USP Controlled Room Temperature].
Mfd. by:Taro Pharmaceutical Industries Ltd. Haifa Bay, Israel 26110
Dist. by: Taro Pharmaceuticals U.S.A., Inc. Hawthorne, NY 10532
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